The R tag on stackoverflow.com hit a milestone yesterday: 5000 questions about the R language. (The 5000th question was about the fortunes package, incidentally — thanks to Andrie de Vries for pointing this out on Twitter.) Stackoverflow.com continues to be an excellent resource for R users, and the number of questions (and answers!) continues to grow: 5020 at this writing, and with 1200 users actively following the tag. For comparison, Matlab has about 4400 questions; SAS has 327, and SPSS has 52.
There are also 735 questions tagged with r on the “stats” stackexchange, for general questions about statistics.